Ventilation and Indoor Air Quality

What Role Does Ventilation Play in a Commercial or Industrial Building?

Ventilation is responsible for indoor air renewal, contaminant removal, and humidity control. In commercial and industrial buildings, it is subject to specific regulatory requirements and directly impacts occupant health, productivity, and energy costs.

In Québec, this goes beyond comfort: Division XI of the Regulation respecting occupational health and safety (RSST) sets specific obligations for ventilating establishments, for fresh air change rates, and for maintenance. And a ventilation network drifts quietly — a damper moved during renovation work, a loaded filter, a slack belt, a partly blocked air intake. The building falls away from its design airflow with nothing on a panel to say so, and the first signal is usually an occupant complaint rather than an alarm.

What Ventilation Services Do We Provide?

• Preventive maintenance — duct inspection, filter cleaning, airflow verification, and controls calibration
• Repair — replacement of motors, belts, bearings, and control components
• Installation — commissioning of exhaust fans, air exchangers, and air handling units
• Optimization — airflow balancing, scheduling adjustments, and heat recovery improvements
• Air quality assessment — airflow measurement, CO2 monitoring, and relative humidity evaluation

What Ventilation Equipment Do We Cover?

• Industrial and commercial exhaust fans — belt tension and wear, sheave alignment, listening to bearings, wheel cleaning: dust or grease build-up unbalances the wheel and cuts airflow long before it starts making noise
• Air exchangers and heat recovery ventilators (HRVs) — core and filter cleaning, condensate drain, and above all a check of the defrost sequence: in the Montréal climate, exhaust air cooled below freezing frosts the core and progressively chokes off the fresh air supply
• Energy recovery ventilators (ERVs) — the same items, plus the condition of the moisture transfer media or enthalpy wheel, its drive, and its perimeter seal
• Air handling units (AHUs) — filter pressure drop, coil cleanliness, actual travel of the outdoor air and return dampers and their actuators, condensate pans and traps
• Hoods and specialized exhaust systems — capture at the source, duct condition, and the item most often overlooked: enough make-up air for the hood to actually exhaust
• Pressurization systems — balance between exhausted air and make-up air, confirmed by a differential pressure reading between zones

What Gets Measured During a Ventilation Assessment?

A serious assessment replaces impressions with instrument readings:

• Airflow — with a flow hood at the grilles, a Pitot tube in a straight duct run, or a hot-wire anemometer when velocity is too low for velocity pressure to be readable. This is the starting point for any air balancing work.
• Static and differential pressure — static pressure across the fan locates the true operating point on its curve; the pressure difference between zones exposes the negative pressure pulling air from one space into another.
• Filter pressure drop — read across the filter bank, it tells you when to change the media and governs which MERV rating the installed fan can realistically carry.
• CO₂ and relative humidity — CO₂ works as an indicator of fresh air supply relative to actual occupancy; it is the rise over an occupied day, more than any single reading, that tells the story. As a regulatory benchmark, Schedule I of the RSST sets a time-weighted average exposure value of 5,000 ppm over 8 hours for carbon dioxide — an occupational exposure limit, far above what a properly ventilated office space reads.
• Outdoor, return, supply, and exhaust air temperatures — on an HRV or ERV, these four points give the recovery efficiency the unit is actually delivering, not the one on the data sheet.

Which Common Failures Point Back to Ventilation?

Several of the breakdowns we get called out for start on the airflow side rather than in the equipment being blamed:

• Frozen coils on an air conditioning system — loaded filters, a closed damper, or a slack belt: airflow drops, the coil falls below freezing, and ice blocks what little passage was left.
• A rooftop unit that won’t heat — low supply airflow drives the temperature in the heating section up until the limit control trips; the lockout that follows looks like a burner failure when the problem is on the air side.
• A carbon monoxide alarm — exhaust oversized relative to make-up air puts the room under negative pressure and can interfere with venting of combustion products. The RSST is explicit here: combustion products from an establishment’s air heating facilities must be evacuated directly outside by means of a duct.
• Localized condensation and mold — a pressure imbalance drives humid air into walls and ceilings. Measuring airflow and relative pressures finds the cause where a visual inspection only shows the consequence.

What Do Québec Regulations Require for Workplace Ventilation?

Division XI of the Regulation respecting occupational health and safety governs ventilation in establishments. The requirements that come up most often on our calls:

• Annual inspection — mechanical ventilation systems must be inspected and adjusted at least once a year, with filters maintained or replaced as the need arises.
• Fresh air changes — a mechanical ventilation system must be able to furnish the minimum number of air changes per hour set out in Schedule III, according to the classification of the establishment. The rate follows the activity: a garage for maintenance and repair sits at 4 air changes per hour, a garage for parking and storage at 3 with permanent employees and 2 without.
• Natural ventilation — where it provides the overall ventilation, the ventilation area (windows, shutters, or vents) must reach at least 5% of the floor area in laboratories and office buildings, and 2% in any other establishment.
• Air intakes — they must be placed so as not to draw already contaminated air into the establishment, and the fresh air intake so as not to pull back in air that has just been exhausted. Worth re-checking after any expansion or after a new roof vent goes in.
• Capture at the source — any localized source of dust, gas, fumes, vapours, or mists at a stationary work station must be fitted with a local exhaust ventilation system.

These operating obligations sit on top of the building requirements that applied when the facility was built or altered. Our reports record measured airflow, filter pressure drop, and the condition of drive components — the traceability that lets you show the maintenance was done.

Areas Served

Our ventilation services cover commercial, industrial, and institutional facilities across Grand Montréal, Rive-Nord, and Rive-Sud: office buildings, retail spaces, warehouses, shops and garages, schools, and multi-residential buildings.